eMedExpert Home > Medications Facts > Cephalexin (Keflex)

• Respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes
• Otitis media due to Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcusaureus, Streptococcus pyogenes, and Moraxella catarrhalis
• Skin and skin structure infections caused by Staphylococcusaureus and/or Streptococcus pyogenes
• Bone infections caused by Staphylococcusaureus and/or Proteus mirabilis
• Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae

• Advantages:
• excellent safety record
• very low incidence of allergic reactions
• may be taken without regard to food
• superior to penicillin in the streptococcal throat infection 2
• Disadvantages:
• short half-life requires QID dosing
• less active than cefatrizine and cefaclor against Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis 2

Cephalexin mean half-life is 50 to 80 min. It may take 4 to 5 hours to clear out of the system.

• Cephalexin (Keflex) versus Other Medications

• 1. Disney FA, Dillon H, Blumer JL, Dudding BA, McLinn SE, Nelson DB, Selbst SM. Cephalexin and penicillin in the treatment of group A beta-hemolytic streptococcal throat infections. Am J Dis Child. 1992 Nov;146(11):1324-7.
• 2. Luh KT, Chao HP, Ho SW, Hsieh WC. Comparison of in vitro antibacterial activity of four oral cephems: cephalexin, cefaclor, cefatrizine and cefadroxil. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi. 1984 Feb;17(1):11-8. PubMed

Published: March 31, 2008
Last updated: January 07, 2010